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Major Functions
• Digestion- Break down food into the nutrients the body can absorb.
• Absorption- Take out nutrients out of the food we eat and deliver it to the cells in our body.
• Eliminate solid wastes that is not needed by the body.
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Digestion
• Processing of food• Types
– Mechanical (physical)• Chew• Tear• Grind• Mash• Mix
– Chemical- uses catabolic reactions and enzymes to break down food
• Saliva• Stomach Acids• Bile used to break down fats
Examples of Mechanical Digestion
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Digestive System Organization
• Gastrointestinal (Gl) tract– Tube within a tube– Direct link/path between organs– Major Organs:MouthPharynx Esophagus Stomach Small Intestines
Large Intestines Rectum
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Digestive System Organization
• Accessory Organs– Not in tube path
– Organs• Teeth
• Tongue
• Salivary glands
• Liver
• Gall bladder
• Pancreas
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Mouth- where digestion beginsTeeth- Mechanical Digestion
Salivary Glands- Chemical digestion of compounds such as starch
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Deglutition (swallowing)
• Sequence– A. Voluntary stage
• Push food to back of mouth
– B. Pharyngeal stage• Raise pallate
- C. Esophageal stage- Contract pharyngeal muscles, open esophagus, start peristalsis
Peristalsis__________________
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Esophagus
• Usually collapsed (closed)
• Functions– Secrete mucous
– Transport food to the stomach
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Esophagus
• Sphincters– Upper
– Lower
• Abnormalities– Achalasia
– Atresia
– Hernia
– Barret’s esophagus
– Esophageal varices
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Stomach
• Usually “J” shaped• Mucous membrane
– G cells – make gastrin
– Goblet cells – make mucous
– Gastric pit – Oxyntic gland – Parietal cells – Make HCl
– Chief cells – Zymogenic cells• Pepsin
• Gastric lipase
Very Acidic, but the cells are produced faster than they die
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Stomach
• Functions1. Mix food- Mechanically
2. Reservoir- Store food
3. Start chemical digestion of• Protein
• Nucleic acids
• Fats
4. Destroy some bacteria
5. Absorbs• Alcohol
• Water
• Lipophilic acid
• B 12
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Stomach
Function- To mix, break down (chemically and mechanically), and store food.
• Inner surface thrown into folds – Rugae
• Contains enzymes that work best at pH 1-2 (VERY ACIDIC)
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Small Intestine
• Function- Major site of chemical digestion and absorption.
• Movements– Peristalsis
• Absorbs– 80% ingested water– Vitamins– Minerals– Carbonates– Proteins
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Small Intestine- Accessory Organs
• Liver- Creates bile that is used to break down fats.
• Gal bladder- Stores bile and releases it into the small intestines
• Pancreas- Creates pancreatic juices that neutralize the chyme.
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Large Intestine
Function- To reabsorb water from digested wastes to make solid wastes.
- No villi– No permanent circular folds– Smooth muscle
•Chyme dehydrated to form feces
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Feces Formation and Defecation“whats in it?”
• Chyme dehydrated to form feces
• Feces composition– Water– Inorganic salts– Epithelial cells– Bacteria– Byproducts of digestion
Defecation– Peristalsis pushes feces into
rectum– Rectal walls stretch until full
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http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html
Video of the digestion of food- The whole picture
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Digestive Disorders
Chrone’s Disease (inflammatory bowel syndrome)- Inflammation of the intestines
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Digestive disorders
Blind loop syndrome-Blind loop syndrome occurs when part of the intestine becomes bypassed, so that digested food slows or stops moving through the intestines. This causes bacteria to grow too much in the intestines and leads to problems in absorbing nutrients.
Diarrhea- increased frequency of watery feces. Causing dehydration and abdominal pain.
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Digestive DisordersPhenylketonuria (PKU)- is a rare condition in which a baby is born without the ability to properly break down an essential amino acid called phenylalanine.
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Symptoms
•Lighter skin and hair color
•Delayed mental and social skills
•Bad breath and odor from skin and urine.